In a normal field of vision, the two eyes perceive views of the world from two different perspectives due to their spatial separation within the head. The images from these two perspectives are then recognized as a stereoscopic image by the brain due to parallax of the two images. By utilizing this principle, there has been developed a liquid crystal display in which 3D (three-dimensional) display is carried out by parallax generated by causing an observer to see images from two different points of view through the right eye and the left eye, respectively.
In some 3D liquid crystal displays, images from different points of view are supplied to the respective eyes of the observer by first encoding the left eye image and right eye image on the display screen according to e.g. color, polarization state, or display time, and then separating these images through a filter system of glasses worn by the observer. In this way, only images intended for the respective eyes are supplied to the left eye and right eye of the observer.
In other liquid crystal displays, a display panel 101 is combined with a parallax barrier 101 having a light-transmitting region and a light-shielding region arranged in a stripe pattern. This allows an observer to recognize a 3D image without using a visual assistance such as the filtering system (autostereoscopic display). Specifically, a parallax barrier 102 gives specific viewing angles to the right eye image and left eye image generated by the display panel 101 (see FIG. 8(a)). When viewed in a specific spatial viewing range, only images intended for the respective eyes are viewed by the observer, and a 3D image is recognized (see FIG. 8(b)).
Such a liquid crystal display device that carries out autostereoscopic display by using the parallax barrier is disclosed in U.S. Pat. No. 6,055,013 (Date of patent: Apr. 25, 2000) or Japanese Laid-Open Patent Publication No. 95167/1999 (Tokukaihei 11-95167, publication date: Apr. 9, 1999), for example. In U.S. Pat. No. 6,055,013 (Date of patent: Apr. 25, 2000), a patterned retardation plate is used as the parallax barrier.
Such a liquid crystal display employing a parallax barrier is also disclosed in U.S. Pat. No. 6,046,849 (Date of patent: Apr. 4, 2000), for example. In the liquid crystal display disclosed in this publication, 3D display and 2D display (two-dimensional display) are electrically switched by providing a switching liquid crystal layer or the like as a means of activating and inactivating the effect of the parallax barrier. That is, in accordance with ON/OFF of the switching liquid crystal layer, the display of U.S. Pat. No. 6,046,849 (Date of patent: Apr. 4, 2000) performs 3D display when the effect of the parallax barrier is activated, and performs 2D display when the effect of the parallax barrier is inactivated.
Meanwhile, in these years, a transflective liquid crystal display has been developed, which allows both reflective display and transmissive display on a single display screen. This type of transflective liquid crystal display serves as a reflective display when used in bright surroundings, so that desirable display can be carried out using ambient light without consuming much power. In dark surroundings, the liquid crystal display serves a transmissive display, so that desirable display can be carried out using the backlight.
Conventional transflective liquid crystal displays commonly adapt a system as disclosed in U.S. Pat. No. 6,195,140 (Date of patent: Feb. 27, 2001). The liquid crystal display (disclosed in U.S. Pat. No. 6,195,140 (Date of patent: Feb. 27, 2001) has a structure in which, as shown in FIG. 9, pixel electrodes are disposed in a matrix through switching elements (not shown) at respective intersections of gate bus lines 111 and source bus lines 112 that are mutually orthogonal.
The pixel electrodes include a transparent electrode and reflective electrode which are electrically connected to each other. The transparent electrode is formed on a transparent insulating layer (not shown) formed on the gate bus lines 111, the source bus lines 112, and switching elements. The reflective electrode has an aperture for light transmission, and is formed on the transparent electrode. In the liquid crystal display, reflective display is carried out in a region 113 where the reflective electrode is formed (that is, a reflective region: shaded region in the figure), and transmissive display is carried out through a transmissive region (projected region in the figure) 114, i.e., the aperture formed through the reflective electrode.
In the liquid crystal display carrying out reflective display, microscopic irregularities are formed to prevent an image from reflecting on the reflective electrode. The irregularities formed on the reflective electrode should be randomly disposed. However, for simplicity of the process, the irregularities are formed by a recurrent pattern. When the recurrent pattern of the irregularities is periodic, the reflecting light at the reflective electrode generates a periodic interference pattern, called moire, which deteriorates image quality.
In order to solve moire, in liquid crystal displays carrying out reflective display, normally, a diffuser process is carried out. In the diffuser process, fine particles are added to an adhesive layer which is used to attach a polarizer to the display surface side of a liquid crystal display panel, so that moire can be prevented by the light scattering effect of the fine particles.
However, in the conventional arrangement, the following problem occurs when the 2D/3D switching display function and the transflective function are used in combination in the same liquid crystal display panel.
As described with reference to FIG. 8 above, 3D display utilizes linearity of light emitted from the backlight and transmitted through the liquid crystal display panel. Therefore, in 3D display, only the transmissive region of each pixel is used, and the reflective region is not used at all. Also, when 2D display is performed, since the diffusing process for preventing moire is performed over the entire liquid crystal display panel, its effect also covers the transmissive region.
However, since the diffuser process gives the scattering effect to the light that emerges from the display surface side of the liquid crystal display panel, the display performance of 3D display utilizing linearity of light deteriorates significantly when the scattering effect is given to the outgoing light from the transmissive region of the liquid crystal display panel.
In other words, when the 2D/3D switching function and the transflective function are used in combination in the same liquid crystal display panel, desirable 3D display cannot be obtained while at the same time preventing moire in 2D display.